Many communication systems employ means for delivering messages according to a specified quality of service (QoS). In some cases, a QoS may define a time by which a message is to be delivered to its destination. Alternatively, or in addition, QoS parameters may affect how a message is handled at intermediate stations between its sender and its destination. Most generally, a QoS policy sets forth requirements a network must provide to an individual flow of information (eg, a voice call, an interactive video conference, a data file transfer) so that the information is optimally delivered.
Quality of service may be a measure of performance for a transmission system that reflects it's transmission quality and service availability. On the Internet and in other networks, QoS encompasses the notion that transmission rates, error rates, and other characteristics can be measured, improved, and, to some extent, guaranteed in advance. QoS is of particular concern for the continuous transmission of high-bandwidth video and multimedia information because transmitting such content dependably is difficult in public networks using ordinary “best effort” protocols.
Quality of service policies are often implemented as hard-coded circuit characteristics of a message communication system. Thus, once specified as part of a communication system design they cannot be modified. Indeed even where soft-coding is used to specify QoS parameters, once an information flow has commenced changes to such QoS are not easily made. At the same time, offerings such as application programs and the like are contiually changing over time and, so, there is a need to dynamically adapt document transport QoS.